Heat accumulators for storing large quantities of thermal energy from power plant capacities are typically used as seasonal accumulators for the temporary storage of surplus energy from the power generation. Thus, for economical reasons it can be proved to be advantageous to temporarily store surplus energy—which is generated outside of the peak load times—in thermal form. The surplus energy can be extracted from conventional power generation or also be provided by means of regenerative power generation, especially thermosolar power generation.
From DE 10 2004 019 801 A1 it is known, for example, to temporarily store thermal energy from a gas flow by means of a gas-sand heat exchanger. The heat transfer is carried out in this case in a shaft which has porous walls which are connected to a gas inlet or gas outlet. Located inside the shaft is a sand section which ensures that the sand located therein is moved through the shaft at an adjustable speed. During operation of the gas-sand heat exchanger hot gas flows through the porous shaft wall into the chamber which is filled with sand and via direct heat contact partially transfers the heat energy to the sand grains. After that, the thereby heated sand can then be stored in a suitable manner and made available again to a heat extraction at a later time for a thermal reconversion application, for example.
However, the relatively cost-intensive operation of such a plant is disadvantageous to such a heat accumulator since the sand also has to be re-manipulated during extraction of the thermal energy in order to transfer its thermal energy to a flowing medium. Furthermore, an only relatively small quantity of heat can be transferred to the sand as heat storage medium, i.e. a relatively high power loss is to be taken into consideration. What is proved to be a further disadvantage of such a plant which is known from the prior art is that it has movable machine parts which can be vulnerable and therefore very maintenance intensive. This in turn results in undesirable downtimes and therefore financial losses on the part of the operator of such a plant.
Further disadvantages of the heat accumulators which are known from the prior art lie in their high costs for achieving an adequate thermal insulation. Even in the storage of thermal energy at a relatively high temperature level (>100° C.) in comparison to typically prevailing ambient temperatures the costs for the provision of an adequate insulation proves to be high. Since, moreover, heat accumulators for the storage of surplus energy from power plant capacities are of relatively large dimensions, the costs for achieving an adequate thermal insulation are sometimes crucial to whether the heat accumulator can be operated economically or not.